Grand Theft Auto Vice City Walkthrough :
Demolition Man

This can be very frustrating if you're not patient. Practice a few times with the helicopters to learn how they work. Your aim is to bring four bombs to four different spots in a building - one per level. You have to fly the helicopter up the stairs to get to each level.

Turn with R2/L2 and NOT the stick. Use the stick for forward motion, and tap X to get the height you want. Remember where the bombs are - they're not marked on the map!!

You have 7 minutes - plenty of time. Just go slow and steady, don't try to rush. Start at the bottom and work your way up, doing tight corners up the stairs with the R2/L2. You'll have a full 2:45 for the last bomb so take it slow and you'll do fine.

Payoff: $1000
Tip from Midnight:
As the timer will NOT start until you pick up the 1st bomb, carefully fly the helicopter around the building, flying straight at the builders (the rotors will kill them). This way you can both remove the dangers to the chopper AND work out exactly where the bombs need dropping. Then go back and collect the 1st bomb. MUCH easier.